In high resolution balances the air buoyancy, to which the sample to be weighed is subject, has an effect on the accuracy of the measurement results. Therefore, for measurements of ultra high accuracy it is necessary to determine the air density in order to determine an air buoyancy factor. For precision balances it is known, for example, that the air buoyancy correction factor is determined by a comparison measurement of two reference objects having a mass and density that are already known beforehand.
It is also known that the temperature, the air pressure and the humidity also affect the balance itself, in particular, the load cell. For this reason, in order to compensate for the variances in the balance display with changing ambient parameters, correction factors are stored in the device, for example, in the form of curves or tables. In addition, temperature and air humidity sensors are disposed, in particular, in the surrounding area of the load cell. Then these temperature and air humidity sensors are used to automatically correct the balance itself, as a function of the changing ambient conditions, also called climate changes.
Thus, the German patent DE 37 14 540 C2 describes a method for automatically calibrating a high resolution electronic balance, wherein such environmental factors as the temperature change and the humidity change, both of which are detected from the outside, are used to calibrate the balance itself. The corresponding calibration factor is determined by a computer and corrects the weighing result.
The German patent DE 299 12 867 U1 discloses an analytical balance with a measuring sensor for ambient parameters. In this case the analytical balance has a display that is provided on the rear wall of the weighing chamber. The display shows the temperature in the weighing chamber and the air humidity in the weighing chamber as well as in general the air pressure that is usually present. In this case it is assumed that, when the air is wet, the surface of the sample to be weighed will be covered with moisture, which is a function of the variances in the air humidity. Therefore, the operator is informed by the display that, for example, with changing air humidity, the sample to be weighed should remain in the weighing chamber longer, in order to obtain a stable end value of the surface moisture. If there are extreme fluctuations in the air pressure, then the operator can perform a so-called buoyancy correction by feeding the displayed data to a processor in the balance via an input unit. With respect to the temperature, this temperature is used to determine the deviation from the reference temperature and to consider corresponding correction factors.
Finally there are also climatized measuring chambers, in which there are precision balances, into which the climate data of the measuring chamber are entered. The climate data from the climate module or the sensors thereof are fed manually or automatically into the balance.